1. Field of the Invention
The present invention relates generally to turbines for creation of electrical power, and more specifically to horizontal wind turbines.
2. Description of the Prior Art
Throughout history, civilization has yearned for better and more efficient sources of power generation. Fossil fuels have not always locally available and have been expensive to transport over long distances. Nuclear power has produced unwanted radioactive waste and carries potential for apocalyptic accidents. Solar power's promise has been dimmed by the high cost of equipment necessary to utilize the sun's energy. Hydroelectric power generation requires flowing water and, often, disruption of normal paths of water. Seemingly, the wind is the only readily available and safe source of power.
Though developed centuries ago, wind-powered devices are thus still a favored source of power generation today. The windmill, once used to grind grain, has been adapted to produce electricity. Windmills have evolved into wind turbines wherein the wind's power no longer turns stone wheels atop grain, but rather passes magnets alongside wire coils to generate electricity. In wind turbines, the wind's force pushes the blades of a wheel which act as the rotors of a generator.
Over time, wind turbines have been developed to work more efficiently in compensating for many of the natural obstacles impeding consistent energy recovery from the wind. For example, shifts in wind direction can stop a fixed wind turbine; thus, wind turbines have been constructed with various rotational methods so that the wind will strike the blade in the optimum fashion. Further, wind turbines have been developed whereby fluctuations in wind velocity leave the wind turbine relatively unaffected in both structural integrity and power generation potential.
Horizontal axis wind turbine generators have proven very effective in producing electricity from the wind. Typically, they consist of a nacelle mounted atop a tall tower. The nacelle houses a transmission to increase a rotor's rotational speed to the speed of an electrical generator; some means of power smoothing is necessary to compensate for cyclic fluctuation and wind gusts. The nacelle also incorporates a strong shaft to carry a large rotor hub and blades. Turning in a horizontal plane, the nacelle adjusts to the direction of the wind current to face the rotor into the oncoming wind.
Horizontal axis wind turbines are not without their problems, however. The transmission requires regular maintenance and repair; a major expense in horizontal axis wind turbine design is the transmission. Furthermore, the main shaft must withstand not only the load of the rotor hub and blades, but also the load from oscillations and wind gusts. Additionally, expenses are incurred in reinforcing the tower structure supporting the heavy nacelle.
Another problem with horizontal axis wind turbines is maximizing rotor diameter and the number of rotor blades. Horizontal wind turbine generators usually have a rotor diameter of at least 20 meters, and they are designed with only two or three blades. As a general rule, if a wind turbine has a large number of blades, the rotor's solidity is increased, rotation speed is slower, and less noise is produced. Horizontal axis wind turbines have employed few blades, however, because the design and construction of conventional blades is expensive. Moreover, the increased rotor diameter of horizontal axis wind turbines makes blade control and structural integrity difficult at high wind speeds.
The need arises for a horizontal axis wind turbine of simple construction, low production cost, low maintenance cost, and sound structural integrity.
U.S. Pat. No. 145,970, issued to Emilius Sanderson, on Dec. 30, 1873, shows the concept of supporting two sides of a horizontal axis of a wind-wheel.
U.S. Pat. No. 273,182, issued to Homer B. Sprague, on Feb. 27, 1883, and U.S. Pat. No. 5,161,952, issued to Alfred J. Eggers, Jr., on Nov. 10, 1992, show use of a rim having spokes to support blades. These patents also show an aerodynamic blade shape, as well as the use of blades threaded onto spokes.
U.S. Pat. No. 282,122, issued to Carl F. W. Schramm, on Jul. 31, 1883, shows a windmill that automatically adjusts to changes in wind speed.
U.S. Pat. No. 717,939, issued to Luis Soria Y Hernandez, on Jan. 6, 1903, shows a wind turbine rotating on a wheeled base.
U.S. Pat. No. 1,015,416, issued to Judson A. Bennett, on Jan. 23, 1912, shows a frame structure which supports both ends of a horizontal shaft on which is mounted a windmill's vanes. The center post remains fixed as the outer corners follow a circular track to allow rotation.
U.S. Pat. No. 1,233,232, issued to Albert H. Heyroth, on Jul. 10, 1917, U.S. Pat. No. 1,944,239, issued to Hermann Honnef, on Jan. 23, 1934, and British Patent Document No. 507,555, issued to Clement Lean, on Jul. 13, 1939, show use of a rim of a blade structure, in conjunction with a fixed stator section, to generate electricity.
U.S. Pat. No. 4,323,331, issued to Schachle et al., on Apr. 6, 1982, shows a frame structure in which a turbine support is rotatably mounted on a ground-based support member.
U.S. Pat. No. 4,364,708, issued to Constant V. David, on Dec. 21, 1982, shows a windmill having adjustable blades.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.